The present invention relates in general to forming aluminum, copper or other ductile metals and, more particularly, to methods and apparatus for forming one or more risers on a blank of such material to form, for example, a manifold for a heat exchanger. In an initial application of the present invention for forming a manifold for an automotive air conditioner condenser, the blank includes a siamesed pair of tubular passages to each of which a plurality of tubular risers are formed.
A common form of heat exchanger used for automotive, residential and commercial heating and cooling applications is formed by connecting a number of generally U-shaped tubes to a header plate or manifold. The manifold typically comprises one or two hollow passages with a series of individual tubular risers extending from and being in communication with the passage or passages. The U-shaped tubes are then connected to the manifold by means of the tubular risers.
Numerous arrangements have been used to form manifolds for the manufacture of such heat exchangers. One recent example, U.S. Pat. No. 4,663,812, discloses extruding or drawing a tube with an integral rib formed on one side of the tube. The rib is formed into a plurality of cylindrical solid risers by machining or cold forming with cold forming taking place after insertion of a supporting mandrel or cylinder into the tube. The solid risers are converted to hollow risers by an impact extrusion process. Apertures are then formed under the hollow risers by operation of a cutting or perforating tool on the open tube.
Another later example, U.S. Pat. No. 5,190,101, discloses a heat exchanger manifold made from a one piece aluminum extrusion. The extrusion is a U-shaped channel. The manifold is formed by piercing a plurality of apertures or extruding a plurality of tubular members in a base member of the channel to form fluid conducting passageways therethrough. Up-standing walls of the channel and then rolled toward the center of the base member to form a pair of hollow fluid conduits which are in communication with their respective fluid conducting passageways. A weld seam or braze joint is then formed along the length of the manifold.
A review of these exemplary arrangements shows that several processing steps are necessary for fabrication of manifolds for heat exchangers in accordance with their teachings. Many other earlier arrangements required even more, some substantially more, processing steps. Since manufacturing efficiency, and accordingly expense, are greatly impacted by the number of steps which must be performed to fabricate a manifold, there is an ongoing need to develop manufacturing arrangements which require fewer or more simplified steps. Preferably, these arrangements could also be applied to other applications and forms of manifolds. For example, it would be desirable to be able to efficiently form tubular risers for solid header plates for manifolds using such header plates.